Table of Contents
Advertisement
2.2.
ELECTROMAGNETIC INTERFERENCE FIELDS
There are 2 types of problems which can typically occur on the heart rate signals:
1) Electromagnetic interference: caused by disturbances from sources of electromagnetic noise.
This problems could cause:
•
higher heart rate signal: HR deviate from the real value, typically making it higher.
•
Saturation: in this case the disturbances from sources of electromagnetic noise is so high
that receiver is no longer able to detect any heart rate signal.
Interference may occur near high voltage power lines, overhead lines of electrical railway, electric
bus lines or trams, television, stereo speakers, neon lights, motors, computers, cell phones, air
conditioning systems, electro-medical devices.
Several pieces of equipment with electronic or electrical components, such as LED displays,
motors, and electric brakes, may cause interference with stray signal.
2) Cross-talk: similar to the interference problem, but this is caused by reception of a signal from
another Chest Belt, typically worn by users on adjacent machines, if they are too close together
(less than 1mt radius, on average). This cause HR beats incorrect reading, with usually higher
values, because the 2 signal received from the Chest Belts, can be summed together by the HR
receiver.
2.3.
MECHANICAL VIBRATIONS
Mechanical vibrations may cause slight shifting of the coil, giving rise to transient impulses. If these
transients occur only occasionally they can be easily filtered by SW. However, if the mechanical
vibrations are periodic, they can produce periodic pulses which may be interpreted as correct heart
rate values.
To eliminate or reduce the effects of vibration the receiver is usually housed into a sponge (see pic.
below).
Page 2.2
HR Noise Detector: quick reference – rev. 1.0
Advertisement
Table of Contents
